[quote=@Meta]
<Snipped quote by DarkwolfX37>

Even if I haven't played the other ones?
[/quote]

You don't need to play the first four games to get G.U. It's a sequel but honestly it's better to play it before the //Games. Knowing what happens in them makes certain things better, but they're relatively minor. You might not even run across one of the characters, and learning the cool tie-ins with the //Games after beating vol.3 is almost better than knowing them beforehand.